Discontinuities in quinoa biodiversity in the dry Andes: An 18-century perspective based on allelic genotyping

Abstract

History and environment shape crop biodiversity, particularly in areas with vulnerable human communities and ecosystems. Tracing crop biodiversity over time helps understand how rural societies cope with anthropogenic or climatic changes. Exceptionally well preserved ancient DNA of quinoa (Chenopodium quinoa Willd.) from the cold and arid Andes of Argentina has allowed us to track changes and continuities in quinoa diversity over 18 centuries, by coupling genotyping of 157 ancient and modern seeds by 24 SSR markers with cluster and coalescence analyses. Cluster analyses revealed clear population patterns separating modern and ancient quinoas. Coalescence-based analyses revealed that genetic drift within a single population cannot explain genetic differentiation among ancient and modern quinoas. The hypothesis of a genetic bottleneck related to the Spanish Conquest also does not seem to apply at a local scale. Instead, the most likely scenario is the replacement of preexisting quinoa gene pools with new ones of lower genetic diversity. This process occurred at least twice in the last 18 centuries: first, between the 6th and 12th centuries—a time of agricultural intensification well before the Inka and Spanish conquests—and then between the 13th century and today—a period marked by farming marginalization in the late 19th century likely due to a severe multidecadal drought. While these processes of local gene pool replacement do not imply losses of genetic diversity at the metapopulation scale, they support the view that gene pool replacement linked to social and environmental changes can result from opposite agricultural trajectories.

Ancient genomes reveal early Andean farmers selected common beans while preserving diversity

“…Damage patterns were partially explained by the location of the archaeological sites: all seeds from sites at >2,500 meters above sea level showed less than 10% base misincorporations (with many lower than 5%), whereas the majority of seeds from lower altitude exhibited levels above 15% (Supplementary Figure S6). The observed pattern shows that both favorable environmental conditions and the structure of the seed (e.g., presence of an external cuticle) likely resulted in good DNA preservation, as previously suggested for quinoa seeds from the same sites [19]. A subset of the specimens (Figure 1a,b) was selected for further sequencing based on DNA preservation and representation of age and locations, resulting in a final dataset of 15 ancient bean genomes with coverage from 4.2X to 23.2X in the non-repeated regions (Supplementary Table S1).…”

Social adaptive responses to a harsh and unpredictable environment: insights from a pre-Hispanic andean society

“…This solution, although not very common, has been applied in other arid areas of the world (Passioura andAngus 2010, Schillinger 2016), and contrasts with the practice of irrigation usually adopted by societies facing similar environmental limitations (Spielmann et al 2011). The high-agricultural production in this context was thus achieved through agricultural knowledge based on a thorough understanding of agro-ecological constraints, combined with a collective work of landscape modifications covering vast areas to retain soil and runoff water, but without resorting to costly techniques such as irrigation channels or monumental terracing (Pouteau et al 2011, Cruz et al 2017, Winkel et al 2018. This resource-use strategy was close to the horticulturist and limited labor models of agrarian societies (Hillier and Hanson 1984, Barbaza 2018.…”

Estudio del desarrollo de aleros y cuevas en diferentes regiones y contextos geológicos de la Argentina: hacia una caracterización de patrones y procesos

“…Como ejemplos de sitios de nuestro país se pueden citar tres hallazgos que merecen destacarse: un conjunto de cientos de plumas de aves (López et al 2015), un par de sandalias de cuero, una trenza de pelo humano y un sonajero de mate (Olivera et al 2003), todos en cuevas del NOA y numerosos artefactos de cuero, pelos, vellones y tendones en un alero de Patagonia (Marchione y Bellelli 2013). También se ha registrado una excelente preservación de ADN antiguo en el material vegetal del Alero 1 PP9 (Winkel et al 2018).…”

“…El origen de los reparos rocosos, su evolución temporal, los tipos de rellenos que contienen así como su eventual colapso, responden a factores de control cuyo análisis resulta clave para entender el uso humano de estos espacios en el pasado, su potencial cronológico, los procesos de sedimentación, las discontinuidades estratigráficas y las condiciones de preservación de materiales arqueológicos y tafonómicos (v.g. Strauss 1990;Bar-Yosef et al 1992;Waters 1992;Farrand 2001a;Goldberg y Sherwood 2006). Entre los factores que controlan su desarrollo pueden destacarse la litología y estructura, el contexto geomorfológico, las condiciones climático-ambientales, el bioma, la actividad tectónica y el tiempo.…”